Structural unit

ABSTRACT

A structural unit for a linear actuator has at least one sensor unit. The sensor unit measures at least one deformation characteristic variable of the structural unit. There is also described a linear actuator with such a structural unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. § 119, of Germanpatent application DE 10 2018 209 703.8, filed Jun. 15, 2018; the priorapplication is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention pertains to a structural unit for a linear actuator. Thestructural unit includes at least one sensor unit.

United States patent application publication US 2019/0048988 A1 and itscounterpart international patent application W02017/048788A1 disclose alinear actuator having a tube and a structural unit that is able to beextended from the tube. The linear actuator has a sensor that measures aforce of the structural unit. Further prior art is disclosed bydocuments German published patent application DE 102010050837 A1,Japanese patent application JP 2005201390 A, U.S. patent application US2005/0255186 A1 and its counterpart European patent application EP1595681 A1, and U.S. patent application publications US 2006/0113940 A1and US 2008/0065354 A1.

SUMMARY OF THE INVENTION

The object of the invention is in particular to achieve a highefficiency.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a structural unit for a linear actuator,the structural unit comprising:

at least one sensor unit;

wherein the sensor unit is configured to measure at least onedeformation characteristic variable of the structural unit.

In other words, the sensor unit measures a deformation characteristicvariable of the structural unit. A high efficiency can thereby beachieved. It is in particular possible to draw very accurate conclusionswith regard to a force exerted by the structural unit, in a simple andinexpensive manner.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a structural unit for a linear actuator, it is nevertheless notintended to be limited to the details shown, since various modificationsand structural changes may be made therein without departing from thespirit of the invention and within the scope and range of equivalents ofthe claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a perspective partly sectional view of a linear actuatoraccording to the invention;

FIG. 2 shows a cross section of the linear actuator;

FIG. 3 shows a structural unit and a threaded spindle of the linearactuator;

FIG. 4 shows a perspective view of a cross section of the structuralunit together with the threaded spindle; and

FIG. 5 shows a longitudinal section through the linear actuator.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is shown a perspective, partlybroken-away view of a linear actuator according to the invention. Thelinear actuator has an outer tube 10 and a structural unit 12 that isable to be partly moved out of the tube and back into said tube in astraight line relative to the tube. The movement is brought about by anon-illustrated motor that is able to turn a threaded spindle 40 (see,FIGS. 3, 5), whose center of gravity rests relative to the tube 10,about the tube 10, as a result of which a nut of the structural unit 12,which nut is fixed in relation to a circumferential direction relativeto the tube 10 and into which nut the threaded spindle is screwed, isable to be moved in a straight line together with the entire structuralunit 12 relative to the tube 10.

The linear actuator furthermore has a sensor unit 14 that is designed tomeasure deformation characteristic variables of the structural unit 12.The sensor unit 14 is arranged at a radial outer region 16 of thestructural unit. A tube 42 of the structural unit 12 comprises a wall 18of the structural unit. The wall 18 is formed with a recess 26 in theform of a through-hole of the tube. The sensor unit 14 is arranged inthe recess 26 and bears on a boundary of the recess 26 along acircumference of the recess 26. The sensor unit 14 has the shape of acircular cylinder, but may in principle also have another shape. In aview along a radial direction of the tube 42 onto the recess 26, boththe recess 26 and the sensor unit 14 have a circular shape. As a result,easy and inexpensive manufacturability for both the recess 26 and thesensor unit 14 is ensured.

The sensor unit 14 has a first strain gauge 20 whose longitudinaldirection is parallel to a longitudinal direction of the tube 42 andparallel to a longitudinal direction 24 of the structural unit 12. Ifthe structural unit 12 is extended out of the tube 10, then a force isexerted in the longitudinal direction 24 of the structural unit 12 by anattachment 44 that is part of the structural unit 12 and is attached toan end of the tube 42. The tube 42 is deformed by this force, and so therecess 26 is likewise compressed in the longitudinal direction 24, andthe sensor unit 14 and the strain gauge 20 are thereby also compressedin the longitudinal direction 24. The measurement results of the sensorunit 14 are forwarded to an evaluation unit 22 of the linear actuatorthat is arranged outside the tube 10. The evaluation unit calculates themagnitude of the force from the measurement results. In one alternativeexemplary embodiment, the evaluation unit is arranged inside the tube10. The strain gauge 20 thus measures the magnitude of the extension ofthe recess 26 along the longitudinal direction 24 when force is acting,which constitutes a deformation characteristic variable of thestructural unit 12.

In the present exemplary embodiment, the sensor unit is a module havinga plate girder to which three further strain gauges are attached, inaddition to the strain gauge 20. The four strain gauges are arranged ina full bridge. In one alternative exemplary embodiment, the sensor unit14 has only a single strain gauge.

The structural unit 12 furthermore has three acceleration sensors thatmeasure accelerations of the structural unit 12 that are in each casealigned perpendicular to one another. In alternative exemplaryembodiments, the structural unit 12 has two acceleration sensors or elsejust one acceleration sensor. The structural unit 12 furthermorecomprises a temperature sensor that is arranged adjacent to the nut ofthe structural unit 12.

The linear actuator furthermore comprises a structural unit 32 that isconfigured to transmit data through electromagnetic radiation and thatis designed to wirelessly absorb energy and then electrically supply anelectrical load 34 with the wirelessly absorbed energy. The electricalload 34 in this case is the sensor unit 14. The structural unit 32 alsosupplies itself with electrical energy. The other sensor units orsensors mentioned are likewise supplied with energy by the structuralunit 32. The structural unit 32 is designed as an NFC tag. Energy thatis obtained by the structural unit 32 is buffer-stored by a capacitorfor forwarding to the load 34. Because the structural unit 32 is part ofthe structural unit 12, it is at times arranged inside the tube 10 dueto the ability of the structural unit 12 to move relative to the tube10.

The linear actuator furthermore has an electronic unit 36 that isdesigned to emit electromagnetic radiation in order to transferinformation and in order to transfer energy into an interior of the tube10. The radiation takes place by way of an antenna 38, arranged on andattached to an inside of the tube 10, of the electronic unit (see, FIGS.1, 5). The antenna 38 is part of an NFC reader of the electronic unit.The NFC tag and the NFC reader are each designed to interact with oneanother. To obtain energy, the NFC tag receives electromagnetic wavesthat have been emitted from the NFC reader and converts them intoenergy.

In other exemplary embodiments, NFC reader and NFC tag are replaced withother radio technology structural units having a similar functionalscope. The NFC standard is thus not decisive for the functioning of theinvention and of the exemplary embodiment.

The electronic unit furthermore has a non-illustrated transmission unitthat is designed to transmit information to a receiver remote from thelinear actuator by way of electromagnetic radiation. By way of thistransmission unit, data that originate from the sensor units or thesensors of the structural unit 12, after they have been transmitted bythe structural unit 32 to the electronic unit through electromagneticwaves that are received by the antenna, may be transmitted to the remotereceiver. As an alternative or in addition to the evaluation unit 22,this receiver may have an evaluation unit that evaluates the data. Theelectronic unit may furthermore have a reception unit that is designedto receive information from a transmitter remote from the linearactuator by way of electromagnetic radiation. The remote receiver andthe remote transmitter may be implemented in a single device. By way ofthe remote receiver or transmitter, it is made possible for theelectronic unit to transmit data to the cloud, and the linear actuatoris thereby part of the Internet of Things. The cloud may store thetransmitted data. The linear actuator may furthermore create aconnection to a smart device, such as in particular a smartphone,through the remote receiver or transmitter.

The evaluation unit 22 is designed as a computing unit that is designed,through its software, on the basis of data that the computing unit hastransmitted to it directly or indirectly in at least one operating modeby a sensor of the linear actuator, to determine a recommendation for anexchange time for a mechanical component of the linear actuator. As analternative or in addition, the evaluation unit, which is remote fromthe linear actuator, takes over this determination of a recommendationfor an exchange time.

The load range able to be measured by the sensor unit 14, due to thesensor unit 14 being arranged in the recess 26, depends on the size ofthe tube 42. If the design of the tube 42 is selected appropriately, thedesired load range is thus able to be sensed by way of the sensor unit14 and the strain gauge 20. Of course, the resolution of the straingauge 20 in relation to force determinations also depends greatly on thesize of the tube 42. With a suitable design of the respective tube 42,the same sensor unit 14 and the same strain gauge 20 may therefore beused for linear actuators according to the invention of different sizes.

The strain gauge 20 may be vapor-deposited directly onto a substrate ofthe sensor unit 14. In one alternative embodiment, the strain gauge 20may also be vapor-deposited directly onto the structural unit 12 or thetube 42. It is also conceivable in principle for the strain gauge to bemanufactured through thick film technology.

The data may be transmitted to the receiver, remote from the linearactuator, in particular using radio standards, such as for example usingthe GSM standard or the Bluetooth standard.

In one alternative embodiment of the invention, the electronic unit 36is arranged inside the tube 10.

The electrical connection of the sensor unit and therefore the supply ofpower to and evaluation of the sensors takes place through flexibleelectrical conductors.

In one alternative exemplary embodiment, the sensor unit 14 is attachedto a radial outer surface of the tube 42 by two pins. The sensor unit 14then measures the change in the distance between the two pins.

The following is a summary list of reference numerals and thecorresponding structure used in the above description of the invention:

10 Tube

12 Structural unit

14 Sensor unit

16 Outer region

18 Wall

20 Strain gauge

22 Evaluation unit

24 Longitudinal direction

26 Recess

32 Structural unit

34 Load

36 Unit

38 Antenna

40 Threaded spindle

42 Tube

44 Attachment

1. A structural unit for a linear actuator, the structural unitcomprising: at least one sensor unit; said sensor unit being configuredto measure at least one deformation characteristic variable of thestructural unit.
 2. The structural unit according to claim 1, whereinsaid at least one sensor unit is arranged on a radially outer region ofthe structural unit.
 3. The structural unit according to claim 1,wherein said at least one sensor unit is at least partly arranged in awall of the structural unit.
 4. The structural unit according to claim1, wherein said at least one sensor unit has at least one first straingauge.
 5. The structural unit according to claim 1, wherein thedeformation characteristic variable is a dimension characteristicvariable of a recess formed in the structural unit.
 6. The structuralunit according to claim 1, wherein said at least one sensor unit is atleast one of round or circular in at least one view.
 7. The structuralunit according to claim 1, wherein said at least one sensor unit is afirst sensor unit and the structural unit further comprises at least onesecond sensor unit disposed at a spacing distance from said first sensorunit.
 8. The structural unit according to claim 1, which comprisesflexible electrical conductors enabling an electrical connection of saidat least one sensor unit and a supply of power to and evaluation ofrespective sensors of said at least one sensor unit.
 9. The structuralunit according to claim 1, which comprises at least one sensor selectedfrom the group consisting of at least one temperature sensor and atleast one acceleration sensor.
 10. A linear actuator, comprising astructural unit according to claim
 1. 11. The linear actuator accordingto claim 10, further comprising at least one evaluation unit configuredto calculate a force acting on said structural unit from at least onemeasurement result measured by said at least one sensor unit.
 12. Thelinear actuator according to claim 11, wherein said evaluation unit isconfigured to calculate the force from that at least one measurementresult of said at least one sensor unit and a further sensor unit of thelinear actuator.
 13. The linear actuator according to claim 11, whereinsaid evaluation unit is configured to calculate the force acting in alongitudinal direction of said structural unit.